Abstract [en]

Growth in infrastructure and energy utilization consistently put forward the demand for added quality and quantity of electric power. Reliability concerns over power systems are widespread within its different associated divisions like 'primary' power system structure, protection system, control equipment, ICT (Information and Communication Technologies) etc. This paper is a review of the present status of practices regarding reliability analysis in these divisions and works towards collectively assessing some of the studies in the respective areas. The idea of integrating reliability analysis from the above areas is introduced along with pointing out the major challenges associated. A set of tools for operators to make use in these reliability evaluations and modelling are mentioned. The earlier attempts towards combined overall system reliability analysis are discussed and the approach in this regard with the help of 'control functions' is emphasised. The paper includes works dealing with theory, different methodologies and data associated with power system reliability.

Place, publisher, year, edition, pages

IEEE , 2014. 6960653- p.

Keyword [en]

power system control, power system reliability, powr system modeling, protection system reliability, substation automation

Babu, Sajeesh

Abstract [en]

Power systems are in a phase of automation where intelligent components and sub-systems are employed to monitor, control and manage the grid. Quantifying the complex consequences on system reliability, from the integration of such automated and semi-automated equipment into the existing grid is important for maintenance optimisation and fault mitigation. This thesis identifies the advanced approaches in power system reliability analysis with the potential to capture the complications and correlations in modern power grid after reviewing the traditional reliability evaluation methods.

A method for modelling the different modes of failures, possible in a substation and feeder architecture along with the probable false tripping scenarios was developed. An improved Reliability Block Diagram based approach was designed to count in the traditionally unaccounted failure cases affecting both the primary grid and the protectionand control equipment. The effect and corresponding trend of additional feeder lines in a radial distribution system on the net interruption rate experienced at load ends of feeders are derived and modelled. Such real-world substation architectures are analysed and the aforementioned trends are compared with those from the practical grid. Thus, the analysis was able to identify and measure the complex hidden failure probabilities due to both unwanted operation of breakers and functional failure of protection systems.

The measured probabilities were used to calculate the impact of protection and control equipment on system reliability. The obtained results were verified by comparing it with the observations by energy researchers on ten years of protection system failure statistics. The application of the model and results, in optimal maintenance planning and power network optimisation are identified as the next step.

Babu, Sajeesh

Abstract [en]

Power distribution networks are recognized as the constituent part of power systems with the highest concentration of failure events. Even though the faults in distribution networks have a local effect when compared to the generation and transmission sides, major contingency escalation events are being more frequently reported from this section. The various aspects regarding the reliability and performance of distribution networks are identified as an important topic. Integration of new technologies, automation and increased penetration of distributed generation is expected to make improving and even sustaining high reliability standards a complex task.

This thesis presents developed approaches to quantify and analyze the complex correlated failure probabilities of different failure modes in distribution networks. A theoretical simulation model that relates to real world data to measure false tripping probabilities is developed and tested. More simplified approaches that utilities can exercise with readily available data in fault registers are also established. Optimal configurations that could improve system performance and respective investment costs are analyzed and savings in system reliability at the cost of grid investments are modelled. The optimization helps in prioritizing the most critical investments by considering the system impact of reconfigurations focusing on meeting customer demands and respecting transfer capacities of weak links. The value of existing networks and willingness of the grid owner in investing can be integrated into suggestive alterations to assist decision making in planning and maintenance allocation.

The thesis makes both system specific and generalizable observations from detailed data collection from power utilities. The observations and results have potential in aiding future research by giving important understanding of the reliability impacts of network structures and of control and protection equipment.